Magnetism

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Magnetism
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What is magnetism?

• Force of attraction or repulsion due to electron
  arrangement
• Magnetic forces are the strongest at the poles
• Magnets have two poles North and South

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Magnetic poles and fields

• Magnets always have two poles
• If a magnet is cut it will still have two poles
• Like magnetic poles repel
• Unlike magnetic poles attract
• A magnetic field is the area in which magnetic
  forces act

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Questions

• What two forces are involved in magnetism?
• Which subatomic particle accounts for magnetism?
• Explain the interaction between magnetic poles
  when they are close together.

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Magnetic materials

• Natural magnets have naturally occurring magnetic
  properties ex LODESTONE (magnetite)

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Temporary magnets

• Easy to magnetize
• Lose their magnetism quickly
• Ex Soft iron

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Permanent magnets

• Hard to magnetize
• Stay magnetized longer than temporary magnets
• Ex alnico (cobalt, nickel, aluminum)

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Questions

• How is a temporary magnet different from a
  permanent magnet?
• Give an example of a natural magnet.

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Earths magnetic properties

• Gilbert was a scientist that showed that the
  Earth behaves as a magnet
• The Earths magnetic field is strongest at the
  poles
• Earths magnetic field is called the magnetosphere

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Compasses

• Compasses are used to determine direction
• Compass needles are magnetized and respond to the
  magnetic field of the Earth
• Compasses point to the MAGNETIC POLES OF THE
  EARTH

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Other sources of magnetism

• Magnetic fields of the Earth and other planets
  are related to their cores
• The sun is a source of a magnetic field

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Questions

• Which scientist described the Earths magnetic
  properties?
• Name the devices used to indicate geographic
  direction based on the Earths magnetic field.

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Questions

• What is the name of the Earths magnetic field?
• Where is the Earths magnetic field the strongest?

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Magnetic variation

• Magnetic poles of the Earth are different from
  the geographic poles of the Earth

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Magnetic Induction

• Process by which materials can be magnetized

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What affects magnetic properties?

• Spinning electrons cause some metals to have
  magnetic properties
• Magnetic domains are groups of arranged magnetic
  fields
• Dropping,hammering or heating a magnet will cause
  a magnet to lose magnetic properties

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Electromagnetism

• Discovered by Oersted (scientist)
• Relationship between electricity and magnetism

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Electromagnets

• Temporary magnets
• Magnetism can be turned on and off
• Made by wrapping wire around a piece of iron and
  sending a current through the wire
• Magnetic field is in the same direction as the
  electric current

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Increasing the strength of electromagnets

• Increasing the voltage or current
• Increasing the number of loops of wire

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Questions

• Explain magnetic variation.
• What is electromagnetism?
• Who discovered electromagnetism?
• Name two ways to increase the strength of an
  electromagnet.
• What type of magnet is an electromagnet?

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Electric motors vs. generators

• Electric motors convert electricity to mechanical
  energy in order to do work
• Generators convert mechanical energy to
  electrical energy

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Transformers

• Used to increase or decrease voltage
• Made of primary and secondary coils
• Two types of transformers
• Step-up (increase voltage)
• Step-down(decrease voltage)

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Questions

• How is a generator different from an electric
  motor?
• Name two types of transformers.
• How is a step-up transformer different from a
  step down transformer?
• What are the two parts of a transformer?